All U.S. patents cited within this specification are hereby incorporated by reference. Autotaxin, also known as ATX, ENPP2 or NPP2, short for Ectonucleotide pyrophosphatase phosphodiesterase 2 is an enzyme secreted within the human body. This molecule has been known for generating lysophosphatidic acid (LPA) through conversion of lysophosphatidyl choline (LPC) thereto via lysophospholipase D activity (the removal of choline from the base compound generates LPA). LPA has been realized to contribute to tumor cell growth, unfortunately, as the reactivity within the human body of LPA within certain tissues has resulted, in certain studies, of cancerous growths when present at certain levels. In this manner, then, it has been theorized that the greater the incidence of autotaxin activity within the human body, the greater the possibility of LPA generation. A reduction in the catalytic capabilities of autotaxin to convert the LPC molecule to LPA would theoretically permit an ultimate reduction in possibility of unwanted cell proliferation through reduced LPA presence within a subject's body.
The mechanism of autotaxin in terms of enzymatic activity and catalysis to form LPA resides in its phosphodiesterase capability. LPA can be generated from the cleavage of the phophodiester bonds of LPC, as well as its function as a phospholipase D enzyme (as presented in Formula I):
In extracellular fluids, this enzymatic catalysis removes the choline group from LPC, leaving LPA, which has a tendency to stimulate cell growth and proliferation as well as chemotaxis. From this, it appears that the motility of tumor cells is increased as well, resulting in properties and gene expression within certain cancers (such as, for instance, breast cancer cells), causing further processing into a form that is bioactive and potentially dangerous. Metastasis and oncogenesis of cancer cells appear to occur as well with elevated levels of LPA present within a targeted region.
It has thus been determined that the ability to prevent, or at least reduce, the amount of LPA within human body holds great promise at, likewise, reducing, if not preventing, the onset of certain cancers. It has been theorized, as noted above, that autotaxin modifications may prevent the undesirable conversion from LPC to LPA; the ability to actually accomplish such a result has been elusive, however, at least to the degree necessary for effective broad-scale utilization of such a method. Any modification thereof must exhibit an ability to drastically reduce the activity of autotaxin while also proving to be non-cytotoxic, or, at least, not as cancer promoting as LPA itself.
Past work has been attempted at reducing activity of alkaline phosphatase enzymes, such as Myers and Widlanski (1993) Mechanism-based Inactivation of Prostatic Acid Phosphatase, Science, 262(5138):1451-1453, in terms of reacting 4-halomethylated aromatic phosphate esters therewith such molecules. Such has proven moderately successful, but has not contributed to any reduction in LPA generation as these prior studies were not directed at enzymes involved in LPA production, particularly in terms of LPC conversion thereto. Other suggested routes have been provided with regard to autotaxin inactivation, such as carbacyclic phosphatidic acid, as discussed in Baker, D. L. et al., (2006) Carba Analogs of Cyclic Phosphatidic Acid Are Selective Inhibitors of Autotaxin and Cancer Invasion, J. Biol. Chem. 281:22786-93, all to no avail, however, as these compounds exhibit no propensity to covalently modify autotaxin. Thus, the autotaxin modification reliability of such previously tested compounds has been rather low, unfortunately. Hence, to date, there exists a need to provide effective modifications to autotaxin enzymes for the reduction of LPC conversion to LPA readily and reliably. No such need has been met until now.